1. Industrial Field of the Invention
The present invention relates to a backlight unit which achieves considerably simple and easy replacement of a line light source, such as a fluorescent tube, that must maintain a predetermined positional relationship with respect to a light guide plate or the like, and relates to an electronic apparatus using the backlight unit.
2. Description of the Related Art
As is generally known, liquid crystal display apparatus are used in many display apparatus for use in information apparatus, such as notebook personal computers, because they feature light weight, thin profile, and low power consumption. In recent years, liquid crystal display apparatus having a backlight unit built therein have become dominant with improvements in brightness and colorization in liquid crystal display screens, and for other reasons. The backlight units are roughly classified into the direct-lighting type using a reflecting curtain or the like, and the edge-lighting type using a light guide plate. In most notebook personal computers and the like, edge-lighting type backlight units are adopted because of a strong demand for thinner profiles.
A description will now be given of the structure of a conventional edge-lighting type backlight unit. FIG. 6(a) is a plan view showing the structure of the backlight unit, and FIG. 6(b) is a side view thereof. As shown in these figures, in the edge-lighting type backlight unit, a fluorescent tube 10 is placed on the side of a light guide plate 20, and is wrapped in a reflecting film 30 so that light emitted therefrom is effectively guided to the light guide plate 20. The reflecting film 30 is made of, for example, a PET (polyethylene terephthalate) evaporated with a high-reflectance metal film of silver, aluminum, or the like, a simply white PET, or the like, and both ends thereof are adhered to the upper and lower (front and back) surfaces of the light guide plate 20 by double-sided adhesive tapes 40.
A diffusing plate 50 and a reflecting plate 60 are provided on the upper and lower surfaces of the light guide plate 20, respectively, and are adhered by a tape 70 or the like to the side portion of the light guide plate 20 opposite from the side portion where the fluorescent tube 10 is placed. The diffusing plate 50 and the reflecting plate 60 are not adhered onto the entire surface of the light guide plate 20, but only to one surface thereof in order to prevent warp resulting from the difference in coefficients of thermal expansion.
In general, the fluorescent tube 10 has the shortest service life among the respective components of the liquid crystal display apparatus. For this reason, there has been a demand for a structure that allows the fluorescent tube 10 to be simply and easily replaced.
In the conventional backlight unit shown in the figure, however, since the reflecting film 30 is adhered to the light guide plate 20, it is impossible to simply and easily replace the fluorescent tube 10. That is, it is significantly troublesome to perform operations of peeling the reflecting film 30 off the light guide plate 20, replacing the fluorescent tube 10, and subsequently adhering the reflecting film 30 again to the light guide plate 20. Moreover, the reflecting film 30 may be creased during replacement.
When the fluorescent tube 10 is placed close to the light guide plate 20 or the reflecting film 30, abnormalities may occur in lighting characteristics. For this reason, spacers SP or the like are sometimes provided to place the fluorescent tube 10 in a predetermined positional relationship with respect to the side portion of the light guide plate 20 and the reflecting surface of the reflecting film 30. This further complicates the operation of replacing the fluorescent tube 10.
The present invention has been made in view of the above problems, and it is accordingly an object of the present invention to provide a backlight unit which achieves considerably simple and easy replacement of a fluorescent tube that must maintain a predetermined positional relationship with respect to a light guide plate or the like, and to provide an electronic apparatus using the backlight unit.